Subsea electric installations, such as transformers or frequency converters, are assemblies used under water. These installations can be filled with insulation fluid. During operation of the installation, temperature of the insulation fluid varies, whereby pressure compensation of the medium can be necessary. This can involve use of a pressure compensator, which can be in fluid communication with the interior of the installation. The pressure compensator is provided for receiving excess fluid when the temperature and volume of the fluid increases, and return the fluid back to the installation when the temperature of the fluid is lowered.
One type of pressure compensators is a bottle compensator. The bottle compensator can have a rigid bottle, and a flexible bag residing within the rigid bottle. The flexible bag can be connected to seawater outside the housing. The intermediate state between the flexible bag and the rigid bottle can act as a reservoir for receiving the excess fluid, such as oil, from the installation.
Known solutions for bottle compensators can have a drawback in that they can be poorly suited for arctic conditions where the temperature goes below zero. In such environments, if the installation is raised to the surface of water for maintenance, the existing bottle compensators can be prone to freezing damages.